There is an alternate perspective:
All reservation holders will get artwork.
Line-waiters will receive something else thereafter. It's tricky insofar as getting too personalized from Elon as there were 115,000 of those folk - rather obviates the opportunity for anything hand-signed unless he's even more of a glutton for punishment than he already is (see decidedly non-executive cot next to desk at end of production line). Even if he signs 100 whatevers per day, that's not happening anytime soon. And there's no Signature Model 3 expected, so pretty much the only thing he might sign would be Founders cars, and those are a tad different than 115,000 tokens of appreciation for waiting in line for some number of hours.
Unless and until clarity is provided, I will continue to hold out hope as one of those line-waiter types for a postage-free, handling cost-free, production cost-free toggle-able option at the time of configuration (could be paint, could be supercharging, could be anything, really - and it certainly does not have to be expensive). So simple. Until the accountants get involved of course. After which, said offering will probably end up being a one-size-fits-all standard something or another such as a differently-embroidered cap or mug or scale model - although those scale models can't be all that inexpensive to produce - especially not 115,000 of them. Then again, go price 115,000 custom-embroidered caps sometime. Which brings us back full-circle to the nice, simple postage-free configuration option at the time of ordering. That could actually be treated differently from an accounting perspective as it's happening as part of an actual order/paid for product, yes? I defer to those appropriately degreed and credentialed for that one (configuration option available for $0 at time of purchase versus marketing chotchky for a reservation - if it isn't available to anyone else, who's to say what the value lost is
? Yes, this is why I am not an accountant.
Larger point being that it's entirely possible that the artwork is for everybody and that line-waiters will receive something later (whatever that happens to be). It stands to reason that line-waiters are more likely to be buyers in the end anyway, so for that reason and a multitude of others, there's really no rush.
We have it easy - all we have to do is wait - they have to actually build something - a few hundred thousand times for openers. Yep. I'll wait.